1. Field of the Invention
The present invention relates in general to the field of producing electromagnetic radiation shielding, and in particular, by way of example but not limitation, to producing electromagnetic radiation shielding in electronic devices with non-flat surfaces.
2. Description of Related Art
In our surroundings there are a large number of electromagnetic fields which are formed by electrical machines and electrical equipment, such as radios, TVs, refrigerators, deepfreezers, stoves, electric ovens, computers, car- and pocket telephones, electrical conductors, power tools, lamps and a number of other devices. These electromagnetic fields, which surrounds us every day, probably cause a number of symptoms for people who are allergic to this radiation, in the form of different allergies, cancers or different types and other complains.
There are today different forms and methods for trying to reduce the effect of the electromagnetic field on people through different types of screening methods.
The electromagnetic radiation can be reduced through shielding the radiating unit with a metallic casing, which can contain the electromagnetic field and thereby reduce the risk of injury to people.
These shielding devices can be made, for example, as an enclosing casing, formed of a net of metal wires or of a metallic foil or from a surface which is metallized through vacuum vaporisation or the structural plastic material in the device can be completely or partially mixed with metal fragments.
The protective effect is thus achieved through placing an obstacle in the radiation direction which shields at least at the place where it is desired to avoid radiation from the electromagnetic field or to shield larger surfaces than that.
To produce this shielding is often expensive and complicated and sometimes does not give an esthetically attractive result. To shield, for example, through clothing the electrical devices with a net or foil does not look nice and furthermore makes it difficult to operate and access them. Internal solutions, such as foils moulded-in or mechanically mounted become both expensive and complicated. If a surrounding casing of plastic is constructed with an electrically conductive material baked into the plastic then the casing becomes unnecessarily heavy and furthermore expensive to produce, since the material cost becomes high and the operating time in an injection mould takes a long time. A vacuum vaporisation method is suitable for producing a surface coating of a thin metallic layer. This method causes problems in the form of difficult handling. First the details must be unpacked. Then comes masking of surface which it is not desired to coat with metal, then hanging up on different stands and then introduction into the autoclave which is then evacuated of air in order to produce a vacuum. It is only after this that the metallization through vacuum vaporisation can take place. Thereafter follows demounting of the metallized details, which will be packaged and transported to the manufacturer of the electrical devices. Vacuum vaporisation plants costs many millions of Swedish crowns which add to the cost for each metallized detail. Metallization which is performed with anodisation has similar disadvantages as the vacuum vaporisation method.
All the above described methods are both time-consuming, labour-intensive and expensive at the same time as the quality of the metallic layer developed is not always sufficiently good.
The present invention is intended to solve the above mentioned problems.
It is known in the prior art to transfer a non-cured or undried paint substance to a foundation from a stamp pad which can be coated with paint in different ways. For example the paint can be pressed through a template against a plate where a picture is etched with the exact shape, spread, thickness and colour. A soft and pliable stamp pad them gets this picture through being pressed against this surface and then transfers this to a pre-determined place on a surface of a detail, for example, a pen, a clockface, a toy or some other detail surface, which can be arched, curved or have another simple surface shape. The picture can also be taken from a screen printed picture. The stamp pad is shaped so that it can follow the different shaped surfaces so that the picture is transferred and covers in the best way the whole of its surface so that no part of the picture is left out. This method is known as "tampon-printing".